Methods to detect and quantitate left ventricular dysfunction and myocardial ischemia provide a scientific basis for rehabilitation following myocardial infarction. There are five major objectives of the present work: 1) to utilize advanced radionuclide imaging techniques to characterize changes in ventricular function and myocardial perfusion at specified intervals 7-180 days after infarction; 2) to evaluate the cardiovascular effects of bedrest and exercise training, utilizing new technology to quantitate long-term physical activity; 3) to utilize radionuclide techniques to establish the physiologic basis for exercise-induced "ischemic" ST segment depression recorded during laboratory testing and to use computer-analyzed ambulatory electrocardiograms to confirm the ischemic nature of ST segment depression occurring outside the laboratory; 4) to compare the diagnostic and prognostic efficacy of standard clinical evaluation (resting ECG and x-ray, hospital course, history and physical examination) with functional evaluation (exercise testing, radionuclide imaging techniques and ambulatory electrocardiography) for the detection of mechanical, electrical and ischemic abnormalities soon after infarction; to compare the effct of focused rehabilitation i.e. short-term counseling and home exercise training with standard medically-supervised rehabilitation on medical and psychosocial status following infarction. Our purpose is to evaluate the efficacy of individual components of rehabilitation and to incorporate the most cost effective of these into a widely available model program which is well integrated into standard medical care.